EP3184177B1 - Air cap and nozzle assembly for a spray gun and spray gun - Google Patents

Description

The invention relates to an air cap for a spray gun, in particular paint spray gun, according to the preamble of claim 1, a nozzle arrangement for a spray gun, in particular paint spray gun, according to the preamble of claim 24, a spray gun, in particular paint spray gun, according to the preamble of claim 25 and a spray gun , in particular paint spray gun, according to the preamble of claim 26.

XP055364477 describes an air cap for a paint spray gun, a nozzle arrangement for a paint spray gun and a paint spray gun.

According to the prior art, a spray gun, in particular paint spray gun, has a paint nozzle on its head, which is screwed into the gun body. The paint nozzle often has a hollow cylindrical cone at its front end, from the front mouth of which the material to be sprayed emerges when the spray gun is in operation. However, the paint nozzle can also be conical in its front area. The gun head usually has an external thread, via which an air nozzle ring with an air cap arranged therein is screwed onto the gun head. The air cap has a central opening, the diameter of which is larger than the outer diameter of the paint nozzle cone or the outer diameter of the front end of a conical paint nozzle. The central opening of the air cap and the cone or the front end of the paint nozzle together form an annular gap. The so-called atomizing air emerges from this annular gap, which creates a vacuum on the end face of the paint nozzle in the nozzle arrangement described above, as a result of which the material to be sprayed is sucked out of the paint nozzle. The atomizing air hits the ink jet, which tears the ink jet into threads and ribbons. Because of their hydrodynamic instability, the interaction between the rapidly flowing compressed air and the ambient air, and because of aerodynamic disturbances, these threads and tapes disintegrate into droplets which are blown away by the atomizing air from the nozzle.

The air cap often also has two horns, which are diametrically opposed to one another and project in the outflow direction beyond the annular gap mentioned and the material outlet opening. Two supply holes, ie horn air supply channels, run from the back of the air cap to horn air channels in the horns. As a rule, each horn has at least one horn air duct, but preferably each horn has at least two horn air ducts. Each horn air duct has a horn air opening on its outside, from which the horn air exits. The horn air ducts or openings are generally oriented so that they follow the longitudinal axis of the nozzle in the exit direction show the annular gap, so that the so-called horn air emerging from the horn air openings can influence the air which has already emerged from the annular gap or the color jet or the color mist which has already arisen at least in part. As a result, the originally conical cross section of the color beam (omnidirectional beam) or the color mist is compressed on its sides facing the horns and slightly lengthened in the direction perpendicular thereto. This creates a so-called wide jet, which allows a higher surface painting speed. In addition to the deformation of the color jet, the horn air also aims to atomize the color jet further.

So-called control openings can be made in the front surface of the air cap, radially outside of the central opening. The air emerging from the control openings influences the horn air, in particular it weakens the impact of the horn air on the paint jet. The control air also protects the air cap from contamination by carrying paint droplets away from the air cap. It also helps to further atomize the paint mist. The control air also acts on the round jet and causes a slight pre-deformation as well as an additional atomization.

Such a nozzle arrangement is particularly suitable for use with a spray gun, in particular a paint spray gun, whereby not only paint but also adhesives or lacquers, in particular base and clear coats, can be sprayed both on a solvent basis and on a water basis, as well as liquids for the food industry, Wood preservatives or other liquids. Spray guns can be classified in particular in hand spray guns and automatic or robot guns. Handheld spray guns are mainly used by craftsmen, especially painters, carpenters and painters. Automatic and robot guns are usually used in conjunction with a painting robot or a painting machine for industrial applications. However, it is quite conceivable to also integrate a hand spray gun into a painting robot or into a painting machine.

The spray gun can in particular have the following: a handle, an upper gun body, a compressed air connection, a trigger guard for opening an air valve and for moving the paint needle out of the material outlet opening of the paint nozzle, a round-wide jet regulation for adjusting the ratio of atomizing air and horn air for shaping the paint jet , an air micrometer for setting the spray pressure, a material quantity regulation for setting the maximum material volume flow, a material connection, paint channels for directing the material to be sprayed from a material inlet to the material outlet, compressed air channels, in particular wide jet channels for supplying the horns with air, and omnidirectional channels for supplying the annular gap and of the control openings with air, a hanging hook and an analog or digital Pressure measuring device. However, it can also have other components from the prior art. The paint spray gun can be designed as a flow cup gun with a paint cup arranged above the gun body, from which the material to be sprayed flows into and through the paint channels essentially by gravity and by negative pressure at the front end of the paint nozzle. The spray gun can, however, also be a side cup gun, in which the paint cup is arranged on the side of the gun body, and in which the material is also fed to the gun by gravity and by vacuum at the front end of the paint nozzle. However, the spray gun can also be used as a suction cup gun with a color cup arranged below the gun body, from which the material to be sprayed is sucked out of the cup essentially by means of negative pressure, in particular by utilizing the Venturi effect. Furthermore, it can be designed as a pressure cup gun, in which the cup is arranged below, above or to the side of the gun body and is pressurized, whereupon the medium to be sprayed is pressed out of the cup. Furthermore, it can be a boiler gun in which the material to be sprayed is supplied to the spray gun by means of a hose from a paint container or by a pump.

The nozzle arrangement and spray gun described above have proven themselves over many years. The quality of the spraying result largely depends on the quality of the spray gun used. High quality spray guns are manufactured with high precision and very tight manufacturing tolerances, since even deviations in the range of a few hundredths of a millimeter from the ideal size can have a negative impact on the quality of the atomization and thus on the spraying result. The quality of the atomization is also determined by the precise design of the so-called nozzle set. The nozzle set usually consists of the air nozzle, the paint nozzle and the paint needle. The air nozzle in turn consists of the air cap and the air nozzle ring. Decisive for the spray quality are in particular the diameter of the needle tip, the inner diameter of the central opening in the air cap, the horn air openings and the control openings, the angles of the openings or channels relative to the central axis of the central opening and the orientation of the openings or channels to one another.

A good atomization quality is particularly important for the application of clear and basecoat (Unilack) on vehicles and vehicle parts. In the case of refinishing in particular, inadequate spray quality has a negative impact on the color accuracy and gloss of the coating. Since the repainted vehicle part is often arranged directly next to a part with the original painting, inaccuracies are clearly noticeable here. A complaint from the customer of the vehicle painter makes post-processing necessary, which is time-consuming and costly.

In the course of spray tests, it was found that the quality of the coating not only depends on the fineness of the atomization, but also significantly on the course of the layer thickness of the coating over the length or height of the spray jet or the spray pattern. A spray pattern is usually created by using the spray gun, which is at a certain distance, for example 15 cm to 20 cm, in front of a substrate, for example paper, a paper with a scale, which is provided for creating a spray pattern, or a metal sheet , Paint or varnish is applied to this sheet of paper or sheet metal without moving the spray gun. The spraying time is approx. 1 to 2 seconds. Alternatively, the spray gun can be moved by means of a device, in particular perpendicular to the longitudinal axis of the wide jet with a constant distance from the sheet or paper. The shape of the spray pattern produced in this way and the size of the droplets on the substrate provide information about the quality of the spray gun, in particular about the nozzles.

The layer thickness of the spray pattern can be determined using the methods known in the prior art, for example using layer thickness measuring devices before or after drying the spray pattern, or the paint droplets and their size and position are still on the substrate during the flight, e.g. detected by laser diffraction.

A spray pattern as described above does not have a uniform layer thickness over its length and width. The central core of the spray pattern has a high layer thickness, outside of the core the layer thickness generated is less. The layer thickness transition between the core and the outer area is fluid. If you apply the layer thickness over the length of the spray pattern, there is initially a flat increase from left to right, which marks the outer edge of the outer area. In the vicinity of the core, the layer thickness increases relatively steeply and ideally remains essentially constant over the length of the core, ie a plateau appears. At the edge of the core, the layer thickness drops relatively steeply, followed by a flatter drop towards the end of the outer area. It has been shown that a uniform coating with better quality can be produced, the sharper the transition between the core and the outer region, ie the steeper the course of the layer thickness over the length of the spray pattern during the transition from the outer region to the core region. During the painting process, the painter moves the actuated spray gun in meandering paths, the paths overlapping in a range between 30% and 50% of their height, i.e. the lower or upper third of a path overlaps with the upper or lower third of the previous path . A sharper defined core area enables the painter to apply the core areas of the spray tracks as contiguously as possible during the painting process so that a uniform overall layer thickness is created. However, the transition must not be too steep, as otherwise there is a risk of over-coating, for example Accidental application of twice the layer thickness occurs, which leads to so-called paint runs. Furthermore, the tests have shown that it is advantageous if the abovementioned plateau is as wide as possible, ie the core area of the spray pattern with the maximum layer thickness is as long as possible.

The object of the present invention is therefore to provide an air cap for a spray gun, a nozzle arrangement for a spray pistol and a spray pistol, with which a better coating quality is achieved than with air caps, nozzle arrangements and spray pistols according to the prior art. In particular, an air cap for a spray gun, a nozzle arrangement for a spray gun and a spray gun are to be provided which generate a spray pattern in which the layer thickness increases as steeply as possible over the length of the spray pattern in the transition between an outer region of the spray pattern and a core region and the core of the Spray pattern, ie the area with maximum layer thickness is as long as possible. At the same time, the spray jet should not become too dry despite the larger core area and the transition between an outer area of the spray pattern and a core area should not be so steep that there is a risk of over-coating.

This object is achieved by an air cap for a spray gun, in particular paint spray gun, which has at least one central opening which is delimited by a mouth and two horns, each with at least one inner and one outer horn air duct and one inner and one outer horn air opening, the The distance between the front end of the central opening and an axis which intersects the central axis of the central opening perpendicularly and passes through the center of an inner horn air opening is between 2.4 mm and 2.6 mm and the angle (α) between the central axis of an internal horn air duct and the central axis of the central opening is between 57 ° and 60 °.

This means the shortest distance between the front end of the central opening, ie the center of the foremost surface of the central opening, and the intersection of the central axis of the central opening with an axis which perpendicularly intersects the central axis of the central opening and through the center of an inner one Horn air opening runs. This distance is the so-called drilling height of the inner horn air duct. The inner horn air channels or openings are the horn air channels or openings which are located closer to the central opening of the air cap. In contrast, the outer horn air channels or openings are the horn air channels or openings which are further away from the central opening of the air cap and are closer to the front end of the horn. The inner horn air channels of the two horns of the air cap preferably have the same drilling height. The term "tapping height" does not necessarily mean that the horn air channels have to be drilled into the horns. The term is only due to the state-of-the-art procedure, according to which the horny air channels are drilled into the horns. However, they can also be introduced into the horns using a laser, or the air cap can be produced by means of 3D printing, casting or die casting, the horn air channels and other channels and openings in the air cap being left out. Accordingly, the horn air ducts, like other ducts and openings of the air cap, do not have to have a circular cross-section, but they can also at least partially have a square, rectangular, triangular, oval or other cross-section. In the case of air caps according to the prior art, the tapping height is more than 2.6 mm. A reduction in the drilling height showed one of the above-mentioned desired effects, namely a longer core area of the spray pattern, ie a wider plateau in the course of the layer thickness over the length of the spray pattern.

The object is also achieved by a nozzle arrangement for a spray gun, in particular paint spray gun, which has at least one paint nozzle, and furthermore has an air cap mentioned above.

The object is also achieved by a spray gun, in particular a paint spray gun, which has an air cap or a nozzle arrangement as mentioned above.

Advantageous refinements are the subject of the dependent claims.

Spray tests have shown that the drilling height of the inner horn air ducts cannot be reduced arbitrarily. Although there is a further widening of the above-mentioned plateau, due to the constant material throughput, the sprayed material is distributed over a larger core area and the spray jet becomes too dry. A tapping height of between 2.4 mm and 2.6 mm for the inner horn air ducts has proven to be a good compromise between the broadest possible plateau and sufficient wetness, i.e. the air cap, in particular the control holes, being otherwise the same. sufficient layer thickness. If the drilling height is further reduced, further adjustments to the air cap are necessary.

In the air cap according to the invention, the distance between the front end of the central opening and an axis which intersects the central axis of the central opening and runs through the center of an outer horn air opening is preferably between 6.0 and 6.6 mm, particularly preferably between 6 , 2 and 6.4 mm. As described above, it means the shortest distance between the front end of the central opening, ie the center of the foremost surface of the central opening, and the intersection of the central axis of the central opening with an axis that perpendicularly intersects the central axis of the central opening and passes through the center of an outer horn air opening. This distance is the drilling height of the outer horn air duct. With conventional nozzles, the drilling height of the outer nozzles is about 5 mm to 6 mm. In the present invention, the drilling height was increased, the outer horn air channels or openings were set further out. The length of the horns can remain the same as in the prior art, but the horns can also be lengthened.

The angle between the central axis of an outer horn air duct and the central axis of the central opening is preferably between 78 ° and 82 °, particularly preferably between 79 ° and 80.5 °. The angle has been increased compared to standard nozzles where the angle is less than 75 °. As with the inner horn air ducts, increasing the angle causes the horn air to hit the paint jet harder and thus improves atomization.

In the context of the present invention, the angle between the central axis of an outer horn air duct and the central axis of the central opening is defined as the tapping angle of the outer horn air duct, the angle between the central axis of an inner horn air duct and the central axis of the central opening is defined as the tapping angle of the inner horn air duct . The ratio between the tapping angle of the outer horn air duct and the tapping angle of the inner horn air duct is particularly preferably between 1.2 and 1.6. The tapping angle of the outer horn air duct is therefore 1.2 to 1.6 times as large as the tapping angle of the inner horn air duct.

The distance between an axis which perpendicularly intersects the central axis of the central opening and runs through the center of an inner horn air opening and an axis running parallel to this axis through the center of an outer horn air opening is between 3.3 mm and 5.8 mm, particularly preferably between 3.4 mm and 4.2 mm. This measure is the distance between the inner and outer horn air openings along the central axis of the central opening, i.e. by the difference in the drilling heights of the inner and outer horn air duct. The horn air openings are further apart in the present invention than in conventional nozzles, in which the dimension is generally less than 3 mm.

The inner diameter of at least one inner horn air opening is preferably between 1.1 mm and 1.3 mm, particularly preferably 1.2 mm.

The inner diameter of at least one outer horn air opening is preferably between 1.4 mm and 1.6 mm, in particular 1.5 mm.

As already mentioned above, the distance between the front end of the central opening and an axis which intersects the central axis of the central opening perpendicularly and runs through the center of an outer horn air opening is the so-called drilling height of the outer horn air opening. The ratio between the tapping height of the outer horn air opening and the inner diameter of the outer horn air opening is preferably between 3.8 and 4.5.

Accordingly, the distance between the front end of the central opening and an axis that perpendicularly intersects the central axis of the central opening and passes through the center of an inner horn air opening is the drilling height of the inner horn air opening. The ratio between the tapping height of the inner horn air opening and the inner diameter of the inner horn air opening is preferably between 1.7 and 2.4.

The ratio between the tapping height of the outer horn air opening and the tapping height of the inner horn air opening is particularly preferably between 2.0 and 3.0.

The central axes of the inner and outer horn air channels are preferably perpendicular to the surfaces into which the horn air channels are introduced. This has the advantage that the risk of the drill slipping away when drilling the horn air ducts is less than if the ducts are drilled into a surface which is inclined with respect to the central axis of the drill. The holes can be positioned more precisely. Furthermore, the vertical drilling creates openings with a circular cross section, which is particularly desirable in the present case. If the channels were drilled into a surface which is inclined with respect to the central axis of the drill, openings with an elliptical cross section would be created. The areas in which the holes are made, i.e. the inner surfaces of the horns can be curved.

The air cap particularly preferably has control openings in the region next to the mouth delimiting the central opening. These control openings, which are preferably configured as bores, extend into the interior of the air cap and are supplied with air from there. The air emerging from the control openings, the so-called control air, hits the horn air emerging from the horn air openings and deflects it and fans the horn air jet, ie it widens it and weakens the horn air jet. The control air also acts on the round jet and causes a slight pre-deformation as well as an additional atomization. In both cases, the control air contributes to the further atomization of the paint jet and reduces the contamination of the air cap by spray mist, since it carries it away from the air cap.

In particular, the air cap can each have three control openings arranged on two opposite sides of the central opening, which are arranged in the form of a triangle, a tip of the triangle being oriented in the direction of the inner or outer horn air openings. The control openings can have the same diameter, advantageously between 0.5 mm and 0.6 mm.

An air cap is particularly preferred in which the control openings arranged in the region next to the mouth delimiting the central opening form an angle of 8 ° to 12 ° with the central axis of the central opening. They are preferably inclined in the direction of the spray jet, so that the control air can strike the horn air or the round jet. The angle of the inner, i.e. the control opening located closer to the central opening between 9 ° and 11 °, the angle of the outer, i.e. control openings between 7 ° and 9 ° further away from the central opening.

The central axes of the control openings are preferably perpendicular to the surfaces of the region into which the control openings are introduced. Similar to the horn air openings, this also has the advantage that the risk of the drill slipping away when drilling the control openings is lower than if the channels were drilled into a surface that is inclined with respect to the central axis of the drill. The holes can be positioned more precisely. Furthermore, the vertical drilling creates openings with a circular cross section, which is particularly desirable in the present case. If the openings were drilled into a surface which is inclined with respect to the central axis of the drill, openings with an elliptical cross section would result.

An air cap is preferred in which the inner diameter of the central opening is between 3.5 mm and 3.7 mm. The wall thickness of the mouth delimiting the central opening is preferably between 0.60 mm and 0.75 mm, in particular in its front area.

The opening delimiting the central opening preferably has a conical outer shape, the central axis of the central opening forming an angle of 25 ° to 35 ° with the outer surface of the opening delimiting the central opening. The currents prevailing at the air cap, in particular the spray jet, cause entrainment of ambient air. It must be ensured that sufficient ambient air can always flow in, as otherwise turbulence occurs on the outside of the spray jet, which negatively affects the spray quality. For this reason, in order to make it easier for ambient air to flow in, most of the front surface of the air nozzle is also slightly conical. The area around which the central opening The delimiting mouth, on the other hand, is chamfered in such a way that the surface is slightly lowered in the direction of the mouth delimiting the central opening. The purpose of this chamfer is also to reduce the contamination of the area with paint mist.

An air cap is particularly preferred in which the central axes of an inner horn air opening and an outer horn air opening intersect at a point, this point lying on the central axis of the central opening of the air cap. The inner and outer horn air openings therefore aim at the same point or the same area on the spray jet. Because of the distraction and fanning out, i.e. Widening of the horn air jet by the control air is the actual point of impact or area of the horn air on the spray jet further away from the air cap than this intersection of the central axes of the horn air openings with the central axis of the central opening. Furthermore, it can be the case that the air from the inner horn air openings does not strike the spray jet in the same area as the air from the outer horn air openings.

The distance between the front end of the central opening and the intersection of the central axes of an inner horn air duct and an outer horn air duct is preferably between 7.5 mm and 8.5 mm.

The ratio between the distance from a horn air opening to the intersection of the central axis of an outer control opening with the central axis of the horn air duct and the distance from the intersection of the central axis of the outer control opening with the central axis of the horn air duct to the intersection of the central axis of the horn air duct with the central axis is central opening of the air cap, between 50:50 and 65:35. This means that the central axis of an external control air opening intersects the central axis of at least one horn air opening approximately halfway between the horn air opening and the intersection of the central axis of the horn air opening with the central axis of the central opening or somewhat closer to the central axis of the central opening.

In the air cap according to the invention, the center points of the horn air openings of both horns preferably lie in a line with the center point of the central opening. This means that in the top view of the air cap, a line runs through the center points of the horn air openings and also through the center point of the central opening of the air cap. This line is preferably a center line.

The air cap is preferably made of brass, which is first pressed warm into a shape similar to the finished air cap before it is coated, preferably by a galvanic process. The semi-finished product is then finished by turning various surfaces and drilling the openings. After that, the Air cap connected with an air nozzle ring and attached to a spray gun. Of course, the air cap can also consist of a different material, for example a different metal or plastic, and can be produced by means of a casting or injection molding process or by means of 3D printing, uncoated or coated by means of another coating process.

In a preferred embodiment of the nozzle arrangement according to the invention, the paint nozzle has at least three V-shaped slots on the outside in the region of its front end, the bottoms of the V-shaped slots converging towards the front in the direction of a central axis of the paint nozzle. The depth of the V-shaped slots, i.e. of the slots with a V-shaped cross section increases in the direction of the paint outlet of the paint nozzle. The bottoms of the V-shaped slots can already cut the inside diameter of the paint nozzle before the front end of the paint nozzle, or the bottoms of the V-shaped slots can cut the inside diameter of the paint nozzle essentially exactly at the front end of the paint nozzle. Preferably, however, the bottoms of the V-shaped slots do not cut the inside diameter of the paint nozzle, i.e. at the front end of the paint nozzle, the bottoms of the V-shaped slots are spaced from the inside diameter of the paint nozzle. The V-shaped slots cause an additional atomization of the paint, in addition to the atomization at the central opening of the air cap. The bottoms of the slots preferably form an angle of 30 ° to 45 ° with the central axis of the paint nozzle. The average Sauter diameter (SMD) is the smallest and the uniformity of the atomization is best at this angle of incidence of the atomizing air on the paint jet. The front face of the paint nozzle can be conical, i.e. the paint nozzle widens in the direction of its outlet. The opening angle is preferably between 80 ° and 100 °. The inner surface of the conical end surface preferably does not cut the outer surface of the paint nozzle at the front end of the paint nozzle, but a region of the front end surface between the conical inner surface and the cylindrical paint nozzle outer surface is designed flat. A vacuum can form in this flat area when the atomizing air emerges from the annular gap between the air cap and the paint nozzle, which draws the paint out of the paint nozzle.

The paint nozzle of a nozzle arrangement according to the invention can be designed conically in its front region. This means that the paint nozzle does not have a hollow cylindrical cone at its front end, but the atomizing air is directed into the paint jet essentially at an angle that corresponds to the angle of the outer surface of the conical paint nozzle relative to the central paint nozzle axis. The angle of the outer surface of the conical paint nozzle relative to the central paint nozzle axis is preferably between 30 ° and 45 ° because here, as already described above, the mean Sauter diameter (SMD) is smallest and the uniformity of atomization is best.

The air cap according to the invention is particularly suitable for use in a nozzle arrangement for a spray gun, in particular paint spray gun. It can be used with an air nozzle ring and a paint nozzle with a spray gun. These can be all types of spray guns described above for spraying different media.

The spray gun can have a hollow needle, which can be designed to guide spray material or compressed air. With a hollow needle carrying spray material, for example, a higher material throughput or the spraying of two-component material is possible. For this purpose, the hollow needle is connected directly or indirectly to a material supply. If the hollow needle is designed to be compressed air, it can contribute to the atomization of the spray material by ejecting atomizing air. For this purpose, the hollow needle is directly or indirectly connected to a compressed air supply. In all cases, the hollow needle can be designed to conduct any volume flow. It is known to the person skilled in the art that the throughput depends on the inside diameter of the hollow needle and on the inlet pressure and volume flow.

Furthermore, the spray gun according to the invention can of course also have other components or configurations according to the prior art.

Fig. 1

ein Ausführungsbeispiel einer erfindungsgemäßen Luftkappe im Schnitt,

Fig. 2

eine Draufsicht auf ein Ausführungsbeispiel einer erfindungsgemäßen Luftkappe,

Fig. 3

den schematischen Aufbau eines Spritzbilds einer Standardluftkappe und eines Spritzbilds eines Ausführungsbeispiels der erfindungsgemäßen Luftkappe zusammen mit dem Verlauf der Schichtdicke des Spritzbilds über die Länge des Spritzbilds.

The invention is explained in more detail below by way of example with reference to three drawings. It shows:

Fig. 1

an embodiment of an air cap according to the invention in section,

Fig. 2

2 shows a plan view of an exemplary embodiment of an air cap according to the invention,

Fig. 3

the schematic structure of a spray pattern of a standard air cap and a spray pattern of an embodiment of the air cap according to the invention together with the course of the layer thickness of the spray pattern over the length of the spray pattern.

Fig. 1 shows an embodiment of an air cap 1 according to the invention with two horns 3, into each of which a horn air supply duct 5 with a horn air supply duct central axis 6 is introduced. Fig. 1 does not show the actual proportions of an air cap according to the invention, but is only to be understood as a schematic representation. The air cap 1 has a central opening 7 with a central axis 9, which of a Mouth 11 is limited with a conical outer surface. The horn air supply channels 5 open into inner horn air channels 15 with inner horn air openings 15a and outer horn air channels 17 with outer horn air openings 17a. The horn air channels or horn air openings, which are arranged closer to the central opening 7, are referred to as inner horn air channels 15 and inner horn air openings 15 a; the horn air channels or horn air openings, which are located further away from the central opening 7, are referred to as outer horn air channels 17 and outer horn air openings 17 a. The angle α with which the inner horn air channels 15 are introduced into the horns 3 with respect to the central axis 9 of the central opening 7 differs from the angle β with which the outer horn air channels 17 with respect to the central axis 9 of the central opening 7 in the horns 3 are introduced. The angles α of the inner horn air channels 15 are essentially the same, as are the angles β of the outer horn air channels 17. The angles α of the inner horn air channels 15 are smaller than the angles β of the outer horn air channels 17 Fig. 1 only one angle α and one angle β are shown on opposite sides of the central axis 9.

In the present exemplary embodiment, the central axes 16, 18 of all four horn air ducts 15, 17 meet at a point D which lies on the central axis 9 of the central opening 7. The point C marks the drilling height of the outer horn air channels 17, the point B the drilling height of the inner horn air channels 15. The drilling height of an inner horn air channel 15 is the distance between the front end A of the central opening 7 in the air cap 1 and an axis 21, which perpendicularly intersects the central axis 9 of the central opening 7 and runs through the center of the inner horn air opening 15a. The drilling height of an outer horn air duct 17 is the distance between the front end A of the central opening 7 in the air cap 1 and an axis 23 which perpendicularly intersects the central axis 9 of the central opening 7 and runs through the center of the outer horn air opening 17a . In the present exemplary embodiment, the tapping height of the two inner horn air channels 15 is the same in each case, as is the tapping height of the two outer horn air channels 17.

The central axes 6 of the horn air supply channels 5 are slightly inclined with respect to the central axis 9, ie the horn air supply channels 5 are introduced into the air cap 1 at a slight angle. The reason for this is that the horn air channels 15, 17 should be made as long as possible in order to achieve the longest possible guidance of the horn air, which is why the horn air supply channels 5 should be arranged as far as possible outside in the air cap 1, but at the same time when the horn air supply channels 5 are introduced as far as possible outside in the air cap 1 parallel to the central axis 9 due to a groove 13 in the air cap 1, the outer wall of the air cap 1 would become too thin in this area. Through the inclined horn air supply channels 5, there is a sufficient wall thickness in the area of the groove 13 with a sufficient length of the horn air channels 15, 17. The groove 13, which is preferably circumferential, serves to accommodate an in Fig. 1 Not shown locking ring, by means of which the air cap 1 in a Fig. 1 Air nozzle ring, also not shown, can be secured. The contact surface 19 of the air cap 1 lies against an inner wall of the air nozzle ring, an outer wall of the air nozzle ring lies against the retaining ring in the groove 13. In the contact area between the air cap 1 and the air nozzle ring, the outer diameter of the air cap 1 is somewhat smaller than the inner diameter of the air nozzle ring. As a result, the air cap 1 is fixed in all directions in the air nozzle ring, wherein rotation of the air cap 1 about the central axis 9 is still possible as long as the air nozzle ring is not yet tightened on the spray gun.

Control openings 25 are arranged in the area next to the mouth 11 delimiting the central opening 7. In Fig. 1 only two control openings 25 can be seen, which are arranged on the cutting line through the air cap 1. The control openings 25 extend through the front wall of the air cap 1 to an inner region 27. The inner region can be formed from various conical and cylindrical surfaces. In the assembled state of the spray gun is located in the inner region 27 in Fig. 1 Paint nozzle, not shown, which can be screwed into the gun body. The front end of the paint nozzle or a front cone of the paint nozzle is arranged in the area of the central opening 7 and forms an annular gap with the central opening 7. The paint nozzle can at least partially extend into the central opening 7, the front end can be set back from the central opening 7, be flush with the front end A of the central opening 7 or protrude beyond the front end A of the central opening 7. Air flows from compressed air channels in the gun body via an air distributor ring into the inner region 27 of the air cap 1 and into the horn air supply ducts 5. Which proportion of air is supplied to the inner region 27 of the air cap 1 and which proportion flows into the horn air supply ducts 5 can be Wide spray regulation can be controlled in the spray gun; this is also influenced by the size and design of the compressed air channels. The atomizing air, ie the air that emerges from the inner region 27 of the air cap 1 from the central opening 7 or from the annular gap described above, sucks the material to be sprayed from the paint nozzle, atomizes it and conveys the paint mist in the direction of the object to be coated. At the same time, the air flows from the inner region 27 of the air cap 1 through the control openings 25. The part of the air supplied to the horn air supply channels 5 and horn air channels 15, 17 flows out of the horn air openings 15a, 17a in the direction of the spray jet, acts on it laterally and actually forms it conical beam into an elliptical wide beam. Before that, the so-called flowing out of the horn air openings 15a, 17a Horn air is hit by the so-called control air flowing out of the control openings 25, fanned out, ie widened, weakened and deflected. The control air also contributes to the atomization of the medium to be sprayed and carries the paint mist away from the air cap 1, in particular from the area 29 adjacent to the mouth 11, and thus reduces contamination of this area.

As in Fig. 1 can be seen, the area 29 is inclined directly next to the mouth 11 delimiting the central opening 7. As a result, the front end of the mouth 11 can be set forward from the adjacent area 29 in order to further reduce contamination of the area 29 without lengthening the air cap 1 toward the front. Furthermore, an afterflow of ambient air to the outflow area of the atomizing air is facilitated, which, as already mentioned above, prevents undesirable turbulence in the area of the spray jet.

Fig. 2 shows a top view of the in Fig. 1 Embodiment of an air cap 1 according to the invention shown in section. Fig. 1 shows the embodiment along the in Fig. 2 shown axis of symmetry 31 cut. In Fig. 2 It can be seen that the air cap 1 has three control openings 25, 26 arranged on two opposite sides of the central opening 7. In each case three control openings 25, 26 are arranged in the form of a triangle, a tip of the triangle being oriented in the direction of the horn air openings 15a, 17a. This means that in each case one of the control openings, in the present case the control openings 25, is in a line with the horn air openings 15a, 17a and an imaginary line between the two adjacent control openings 26 is perpendicular to the axis of symmetry 31. In another exemplary embodiment described above which the drilling height of the inner horn air channels is further reduced, two control openings are arranged on two opposite sides of the central opening 7 in the air cap 1. All four control openings lie in a line with the horn air openings, preferably on an axis of symmetry corresponding to the axis of symmetry 31 of the air cap 1. Preferably, as in FIG Fig. 2 also shows the center of the central opening 7 on the axis of symmetry 31 and on another axis of symmetry 35 lying perpendicular to the axis of symmetry 31.

The area 29 next to the central opening 7 or next to the mouth 11 delimiting the central opening 7 differs from that in FIG Fig. 2 Area 33 shown above and below area 29. Area 33 is conical in such a way that the height of air cap 1 decreases towards the outside in order to allow ambient air to flow in to the flow area of the spray jet. The area 29 is inclined in the opposite direction, ie around the mouth 11 delimiting the central opening 7 there is a slight one Well, from which the mouth 11 is offset, whereby contamination of the area 29 is reduced.

Fig. 3 shows in the upper part the schematic structure of a spray pattern 43 of a standard air cap and a spray pattern of an embodiment of the air cap according to the invention and in the lower part the course of the layer thickness of the spray pattern over the length of the spray pattern.

This in Fig. 3 The spray pattern 43 shown has an outer region 37 and a core region 39. The spray pattern drawn in solid lines is the spray pattern which was created with an exemplary embodiment of the air cap according to the invention, or a spray gun which is equipped with an exemplary embodiment of the air cap according to the invention. The in Fig. 3 Dotted area core area 41 shows the core area of a spray pattern which was created with an air cap according to the prior art or with a spray gun which is equipped with an air cap according to the prior art. The outer shape of the outer area of the spray pattern corresponds approximately to the outer shape of the outer area 37 of the spray pattern, which was created with an embodiment of the air cap according to the invention, or a spray gun which is equipped with an embodiment of the air cap according to the invention. For this reason, in Fig. 3 the outer boundary of the outer area of the spray pattern of an air cap according to the prior art is not shown separately. It can be seen from the spray pattern 43 that the spray pattern of an air cap according to the invention has a longer core area compared to the spray pattern of an air cap according to the prior art, but the overall length of the spray pattern is approximately the same. As already mentioned above, the boundaries of the interior and exterior are not clearly defined, but rather fluid.

In the lower part of Fig. 3 A diagram 45 is shown, which shows a layer thickness curve in μm over a measuring position in mm. The auxiliary lines 47 show which measuring point in the diagram 45 is to be assigned to which location of the spray pattern 43. Diagram 45 shows measurement data of a spray test, which is referred to in the diagram and hereinafter as "standard nozzle" with a SATA®jet 5000 RP with a standard air cap, ie an air cap according to the prior art, and with a SATA®jet 5000 RP with a Embodiment of the air cap according to the invention, in the diagram and hereinafter referred to as "new nozzle" were carried out. The course of the layer thickness of the spray pattern created with the standard nozzle is shown in the diagram as a dotted line 49, the course of the layer thickness of the spray pattern created with the new nozzle appears as a solid line 50. The course of the graphs is in Fig. 3 shown smoothed. The spray test was carried out with a 2 bar (29 psi) and a gun inlet pressure Spray distance of 190 mm to the substrate, in the present case a vertical sheet. A spraying robot moved the spray gun at a speed of 150 mm per second with a constant spraying distance in a direction perpendicular to the longitudinal axis of the broad jet generated. The wide jet was aligned vertically, the spray gun was moved from left to right. A 2K solvent-based clear coat was sprayed on. The material throughput of the paint nozzle corresponded to that of a 1.3 nozzle.

A horizontal streak was produced in the spray test, the layer thickness of the spray pattern being measured in the vertical direction in a central region of the stripe. The measuring position 0 mm in diagram 45 corresponds to the position of the central axis 9 in the central opening 7 in the air cap 1 Fig. 1 in front of the substrate to be coated, in this case the vertical sheet. The central axis 9 is perpendicular to the substrate. The minus area of the X axis of diagram 45 shows the layer thickness profile of the spray pattern along a first direction from the measurement position 0 to the outside, for example upwards, the plus area shows the layer thickness profile of the spray image along the opposite direction from the measurement position 0 outwards, eg downwards. The layer thickness of the spray pattern was therefore measured over a length or height of approximately 550 mm.

It can be seen in diagram 45 that with the standard nozzle as well as with the new nozzle on the outside, in Fig. 3 left end of the spray pattern the zero point of the layer thickness is at the same measuring position of approx. -275 µm. Soon after, however, the layer thickness of the spray pattern created with the new nozzle increases more than the layer thickness of the spray pattern created with the standard air nozzle. The core area begins earlier with the new nozzle, ie further outside in the spray pattern than with the standard nozzle. The plateau, ie the area of the spray pattern with approximately the same layer thickness, is wider with the new nozzle than with the standard nozzle. However, it can be seen that the plateau for the new nozzle is lower than the plateau for the standard nozzle. This means that the layer thickness in the core area of the new nozzle is smaller than in the core area of the standard nozzle. This is a consequence of the broader plateau, ie the longer core area, with the same material throughput and the same order efficiency. Nevertheless, coatings of higher quality can be produced with the air cap according to the present invention than is possible with air caps according to the prior art.

In conclusion, it should be pointed out that the exemplary embodiments described only describe a limited selection of design options and thus do not constitute a restriction of the present invention.

Claims (26)

1. Air cap (1) for a spray gun, in particular a paint spray gun, having at least one central opening (7), which is delimited by a mouth (11), and two horns (3), each having at least one inner and one outer horn air duct (15, 17) and one inner and one outer horn air opening (15a, 17a), characterized in that the spacing between the front end (A) of the central opening (7) and an axis (21) which perpendicularly intersects the central axis (9) of the central opening (7) and runs through the centre of an inner horn air opening (15a) is between 2.4 mm and 2.6 mm and in that the angle (α) between the central axis (16) of an inner horn air duct (15) and the central axis (9) of the central opening (7) is between 57° and 60°.
2. Air cap (1) according to Claim 1, characterized in that the spacing between the front end (A) of the central opening (7) and an axis (23) which perpendicularly intersects the central axis (9) of the central opening (7) and runs through the centre of an outer horn air opening (17a) is between 6.0 and 6.6 mm.
3. Air cap (1) according to Claim 1 or 2, characterized in that the spacing between the front end (A) of the central opening (7) and an axis (23) which perpendicularly intersects the central axis (9) of the central opening (7) and runs through the centre of an outer horn air opening (17a) is between 6.2 and 6.4 mm.
4. Air cap (1) according to one of the preceding claims, characterized in that the angle (β) between the central axis (18) of an outer horn air duct (17) and the central axis (9) of the central opening (7) is preferably between 78° and 82°.
5. Air cap (1) according to one of the preceding claims, characterized in that the angle (β) between the central axis (18) of an outer horn air duct (17) and the central axis (9) of the central opening (7) is preferably between 79° and 80.5°.
6. Air cap (1) according to one of the preceding claims, characterized in that the angle (β) between the central axis (18) of an outer horn air duct (17) and the central axis (9) of the central opening (7) is the spot bore angle of the outer horn air duct (17), that the angle (α) between the central axis (16) of an inner horn air duct (15) and the central axis (9) of the central opening (7) is the spot bore angle of the inner horn air duct (15), and that the ratio of the spot bore angle of the outer horn air duct (17) to the spot bore angle of the inner horn air duct (15) is between 1.2 and 1.6.
7. Air cap (1) according to one of the preceding claims, characterized in that the spacing between an axis (21) which perpendicularly intersects the central axis (9) of the central opening (7) and runs through the centre of an inner horn air opening (15a), and an axis (23) that, parallel with this axis (21), runs through the centre of an outer horn air opening (17a) is between 3.3 mm and 5.8 mm.
8. Air cap (1) according to one of the preceding claims, characterized in that the spacing between an axis (21) which perpendicularly intersects the central axis (9) of the central opening (7) and runs through the centre of an inner horn air opening (15a), and an axis (23) that, parallel with this axis (21), runs through the centre of an outer horn air opening (17a) is between 3.4 mm and 4.2 mm.
9. Air cap (1) according to one of the preceding claims, characterized in that the internal diameter of at least one inner horn air opening (15a) is between 1.1 mm and 1.3 mm.
10. Air cap (1) according to one of the preceding claims, characterized in that the internal diameter of at least one inner horn air opening (15a) is 1.2 mm.
11. Air cap (1) according to one of the preceding claims, characterized in that the internal diameter of at least one outer horn air opening (17a) is between 1.4 mm and 1.6 mm.
12. Air cap (1) according to one of the preceding claims, characterized in that the internal diameter of at least one outer horn air opening (17a) is 1.5 mm.
13. Air cap (1) according to one of the preceding claims, characterized in that the spacing between the front end (A) of the central opening (7) and an axis (23) which perpendicularly intersects the central axis (9) of the central opening (7) and runs through the centre of an outer horn air opening (17a) is the spot bore height of the outer horn air opening (17a), and that the ratio of the spot bore height of the outer horn air opening (17a) to the internal diameter of the outer horn air opening (17a) is between 3.8 and 4.5.
14. Air cap (1) according to one of the preceding claims, characterized in that the spacing between the front end (A) of the central opening (7) and an axis (21) which perpendicularly intersects the central axis (9) of the central opening (7) and runs through the centre of an inner horn air opening (15a) is the spot bore height of the inner horn air opening (15a), and that the ratio of the spot bore height of the inner horn air opening (15a) to the internal diameter of the inner horn air opening (15a) is between 1.7 and 2.4.
15. Air cap (1) according to one of the preceding claims, characterized in that the spacing between the front end (A) of the central opening (7) and an axis (23) which perpendicularly intersects the central axis (9) of the central opening (7) and runs through the centre of an outer horn air opening (17a) is the spot bore height of the outer horn air opening (17a), that the spacing between the front end (A) of the central opening (7) and an axis (21) which perpendicularly intersects the central axis (9) of the central opening (7) and runs through the centre of an inner horn air opening (15a) is the spot bore height of the inner horn air opening (15a), and that the ratio of the spot bore height of the outer horn air opening (17a) to the spot bore height of the inner horn air opening (15a) is between 2.0 and 3.0.
16. Air cap (1) according to one of the preceding claims, characterized in that said air cap (1) in the region next to the mouth (11) that delimits the central opening (7) in each case has three control openings (25, 26) that are disposed on two mutually opposite sides of the central opening (7) furthermore has control openings (25, 26) which are disposed in the form of a triangle, wherein a tip of the triangle is aligned in the direction of the inner or outer horn air openings (15a, 17a).
17. Air cap (1) according to one of the preceding claims, characterized in that said air cap (1) in the region next to the mouth (11) that delimits the central opening (7) furthermore has control openings (25, 26) which in relation to the central axis (9) of the central opening (7) enclose an angle of 8° to 12°.
18. Air cap (1) according to one of the preceding claims, characterized in that the internal diameter of the central opening (7) is between 3.5 mm and 3.7 mm.
19. Air cap (1) according to one of the preceding claims, characterized in that the mouth (11) that delimits the central opening (7) has a conical external shape, wherein the central axis (9) of the central opening (7) in relation to the external face of the mouth (11) that delimits the central opening (7) encloses an angle of 25° to 35°.
20. Air cap (1) according to one of the preceding claims, characterized in that the central axes (16, 18) of an inner horn air duct (15) and of an outer horn air duct (17) intersect at a point that lies on the central axis (9) of the central opening (7) in the air cap (1).
21. Air cap (1) according to one of the preceding claims, characterized in that the spacing between the front end (A) of the central opening (7) and the intersection point of the central axes (16, 18) of an inner horn air duct (15) and of an outer horn air duct (17) is between 7.5 mm and 8.5 mm.
22. Air cap (1) according to one of the preceding claims, characterized in that the ratio of the spacing from a horn air duct (15a, 17a) to the intersection point of the central axis of an outer control opening (25) and the central axis (16, 18) of the horn air duct (15, 17) to the spacing from the intersection point of the central axis of the outer control opening (25) and the central axis (16) of the horn air duct (15, 17) to the intersection point of the central axis (16) of the horn air duct (15, 17) and the central axis (9) of the central opening (7) of the air cap (1) is between 50:50 and 65:35.
23. Air cap (1) according to one of the preceding claims, characterized in that the centres of the horn air openings (15a,17a) of both horns (3) are in line with the centre of the central opening (7).
24. Nozzle assembly for a spray gun, in particular a paint spray gun, having at least one paint nozzle, characterized in that said nozzle assembly has an air cap (1) according to one of Claims 1 to 23.
25. Spray gun, in particular paint spray gun, characterized in that said spray gun has an air cap (1) according to one of Claims 1 to 23.
26. Spray gun, in particular paint spray gun, characterized in that said spray gun has a nozzle assembly according to Claim 24.

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